I use two Airport Expresses, of varying vintages, and two Apple TVs (ditto), and one device that has AirPlay connectivity built-in. I used to sometimes have problems with connectivity, but found that the latest Comcast router has made things a lot better - if you have Comcast, you should check with them, as I think you can swap out your router at no cost. Otherwise, just keep your AEs up to date - make sure you apply updates to them and your other devices. And sometimes it just helps to unplug them and plug them back in. Old school, but it can work.
You also asked about alternative devices. Last year's Apple TV had an optical audio out, but the newer ones do not. There are third-party AirPlay receivers, such as this: https://www.amazon.com/ANEWISH-Wireless-Receiver-Airplay-Adapter/dp/B01N5FOVAJ/ref=sr_1_3?ie=UTF8&qid=1513311806&sr=8-3&keywords=airplay+receiver